Add Polymorphic Path Helpers as a rails til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_497 TILs and counting..._
+_498 TILs and counting..._
 
 ---
 
@@ -325,6 +325,7 @@ _497 TILs and counting..._
 - [Params Includes Submission Button Info](rails/params-includes-submission-button-info.md)
 - [Perform SQL Explain With ActiveRecord](rails/perform-sql-explain-with-activerecord.md)
 - [Pretend Generations](rails/pretend-generations.md)
+- [Polymorphic Path Helpers](rails/polymorphic-path-helpers.md)
 - [Read-Only Models](rails/read-only-models.md)
 - [Rescue From](rails/rescue-from.md)
 - [Retrieve An Object If It Exists](rails/retrieve-an-object-if-it-exists.md)

rails/polymorphic_path_helpers.md

@@ -0,0 +1,33 @@
+# Polymorphic Path Helpers
+
+Underlying many of the path helpers that we use day to day when building out
+the views in our Rails apps are a set of methods in the
+[`ActionDispatch::Routing::PolymorphicRoutes`](http://api.rubyonrails.org/classes/ActionDispatch/Routing/PolymorphicRoutes.html)
+module.
+
+The `#polymorphic_path` method given an instance of a model will produce the
+relevant show path.
+
+```ruby
+> app.polymorphic_path(Article.first)
+  Article Load (0.5ms)  SELECT  "articles".* FROM "articles"  ORDER BY "articles"."id" ASC LIMIT 1
+=> "/articles/2"
+```
+
+Given just the model's constant, it will produce the index path.
+
+```ruby
+> app.polymorphic_path(Article)
+=> "/articles"
+```
+
+Additionally, there are variants with `edit_` and `new_` prefixed for
+generating the edit and new paths respectively.
+
+```ruby
+> app.edit_polymorphic_path(Article.first)
+  Article Load (0.6ms)  SELECT  "articles".* FROM "articles"  ORDER BY "articles"."id" ASC LIMIT 1
+=> "/articles/2/edit"
+> app.new_polymorphic_path(Article)
+=> "/articles/new"
+```